278 FOBMICIDJE. 



deeply marked ; the thorax in profile more or less emarginate at 

 this suture ; mefanotum with a long, level, rather flat basal portion, 

 the posterior lateral angles of which are either dentate or entire, but 

 never with spines as in Aphoenog aster, apex truncate ; legs rather 

 long and slender. Pedicel : the 1st node conical, rounded above, 

 the front face curved inwards, and furnished with a tolerably 

 long petiole anteriorly ; 2nd node broader, rounded above, about 

 as broad as long ; abdomen rather depressed, very broadly oval. 



$ med. Closely resembles the max., but is smaller and has 

 the head very much smaller in proportion to the body, pro- 

 portionately also the pronotum is longer, more rounded above, and 

 the mesonotum not so raised. 



min. Still smaller, the pro- and mesonotum form one con- 

 vexity, there is no transverse impression on the latter, and the 

 metanotum is entire, with only the posterior lateral angles of 

 the basal portion somewhat prominent. 



$ . Resembles the max., but the head is smaller, the eyes 

 larger, the ocelli present, the antennal hollows smaller, the thorax 

 very large and massive ; the pronotum vertical, when viewed from 

 above, hidden under the large, slightly gibbous mesonotum; 

 scutellum very large, projecting posteriori y over the metanotum, 

 this latter with a very short sloping basal portion and the apex 

 vertically truncate, flat or slightly concave, entire. Pedicel thick 

 and massive ; the 1st node broad, transverse, its upper margin 

 rounded ; the 2nd node broad, about as broad as long, and attached 

 by its whole posterior face to the abdomen ; abdomen massive, 

 very broadly oval, its anterior margin transverse. Fore wing 

 with 2 cubital cells. 



c? . Head proportionately small, longer than broad and broader 

 posteriorly than in front ; mandibles broad, the masticatory 

 margin dentate ; clypeus narrow, truncate anteriorly ; antennae 

 13-jointed, filiform, the scape short, about equal to the 1st three 

 joints of the flagellum ; eyes large, ocelli present. Thorax, legs 

 and pedicel as in the $ , the first proportionately just as large and 

 massive; abdomen slightly attenuate towards the apex, the 

 external genital lamina broad. 



I have no personal experience of the species of this genus, but 

 Mr. Wroughton records M. instabilis as a harvester. From its 

 close affinity to Holcomyrmex, essentially a harvester, this was to 

 be expected. 



Key to the Species. 



a. Metanotum wholly unarmed M. barbarns, var. 



instabilis, p. 278. 

 o. Metanotum posteriorly distinctly bidentate 



or sub-bidentate M. Mmalayanus, p. 279. 



318. Messor barbarns, Linn. (Formica) Syst. Nat. 12th ed. i (1767), 

 Atta instabilis, Smith, Cat. vi (1858), p. 163, $ rf . 



